Production process of anchoring nail for nuclear power containment vessel

Abstract

The invention discloses a production process of an anchoring nail for a nuclear power containment vessel. The production process comprises the following steps: S1, coiling a material; s2, pickling and phosphating; s3, fine wire drawing is conducted, specifically, fine wire drawing equipment is used for conducting drawing treatment on the wire obtained after acid pickling and phosphating; s4, cold heading forming; the anchoring nail is machined through a cold header and a mold, in the production process of the cold header, the two ends of the anchoring nail are stressed at the same time, and stress caused by the rod portion of the anchoring nail is removed; s5, oil removal: removing oil remaining on the surface of the anchoring nail after cold heading forming; s6, softening and tempering: putting the deoiled anchoring nail into a constant-temperature furnace for tempering, specifically, tempering at the constant temperature of 580 DEG C for 6 hours, and cooling along with the furnace for 8 hours; s7, shot blasting; and S8, rust prevention. The anchoring nail can meet the mechanical property requirement when the anchoring nail is welded with a nuclear power containment steel lining through fine line pulling, cold heading forming and deoiling and then through softening and tempering, and then the quality stability of a nuclear power containment project is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of anchor nail production, and in particular to a production process of anchor nails for nuclear power containment. Background Art

[0002] The steel lining material of the nuclear power containment vessel is Q265HR steel plate specially used for nuclear power. When in use, several anchor nails are welded to the steel plate according to construction requirements.

[0003] Usually, in order to test the mechanical properties of anchor nails, it is necessary to carry out destructive testing after the anchor nails are welded to the steel plate. The test is carried out according to the following standards:

[0004] Tensile test: Take two stacked welded anchor nails as a group for tensile test (stretch the anchor nails in the direction perpendicular to the plate surface), and no fracture damage is allowed on the connecting weld between the anchor nail and the steel plate;

[0005] Bending test: The anchor nails were subjected to a 45° hammer bending test. No cracks or cracks were found on the connecting weld between the anchor nails and the steel plate.

[0006] Metallographic test: Randomly select one of the bending specimens to perform low-magnification metallographic examination on the longitudinal and radial sections of the steel plate and anchor nail assembly; there should be no lack of fusion, cracks and other defects on the cross section of the weld and heat-affected zone.

[0007] Through the above nuclear power welding test, the mechanical performance requirements of the anchor nails are clearly defined:

[0008] Tensile strength: 400MPa<Rm<550MPa;

[0009] Yield strength: 320MPa<Rp0.2<380MPa;

[0010] Elongation: A≥20%.

[0011] Therefore, it is necessary to formulate corresponding production and preparation processes based on the mechanical performance requirements of the anchor nails. Summary of the invention

[0012] To this end, the present invention provides a production process for anchor nails for nuclear power containment to solve the above-mentioned problems in the prior art.

[0013] In order to achieve the above object, the present invention provides the following technical solutions:

[0014] A production process for anchor nails for nuclear power containment, comprising the following steps:

[0015] S1. Material rounding: the raw material is initially processed into a round shape through hot rolling to obtain a billet of suitable size;

[0016] S2. Pickling and phosphating to remove impurities remaining on the surface after the coiling treatment and form a protective film with lubricating effect on the surface of the material;

[0017] S3. Fine wire drawing: Use fine wire drawing equipment to draw the wire after pickling and phosphating, so that the wire becomes thinner until it meets the requirements of the cold heading machine;

[0018] S4. Cold heading: The anchor nails are processed by cold heading machine and mold. During the production process of the cold heading machine, both ends of the anchor nails are stressed at the same time, and the anchor nail rod will cause stress removal, which will lead to different degrees of changes in the mechanical properties of the product.

[0019] S5. Degreasing: removing the oil remaining on the surface of the anchor nail after cold heading;

[0020] S6. Softening and tempering: put the degreased anchor nails into a constant temperature furnace for tempering, specifically: 580°C, 6 hours constant temperature tempering, and cooling with the furnace for 8 hours;

[0021] S7. Shot blasting;

[0022] S8. Rust-proof.

[0023] Further: In S5, the specific method of degreasing is: first preheat the mesh belt furnace, heat the mesh belt furnace to 350-400°C, and then put the anchor nails into the mesh belt furnace to vaporize or burn the oil.

[0024] Further: In S7, the specific steps of shot blasting are: sending the anchor nail into the shot blasting machine, and spraying the steel shot onto the surface of the anchor nail through the high-speed rotating shot blasting impeller; during the shot blasting process, the steel shot will hit the surface of the anchor nail at a very high speed and a certain angle, thereby cleaning and strengthening the surface of the anchor nail.

[0025] Further: In said S8, the specific steps of rust prevention are: soaking the shot-blasted anchor nails in an aqueous rust-proof solution for 1-3 minutes, and then drying them. During the soaking, it is necessary to ensure that each part is fully covered by the aqueous rust-proof solution.

[0026] Further: The specific method of pickling and phosphating is:

[0027] Immersion pickling: Immerse the entire disk into three hydrochloric acid tanks at room temperature and concentration of 10%-25% for 1-8 minutes;

[0028] Removal of corrosion products: The pickled raw materials enter the flowing clean water tank, and the acid remaining on the surface of the material is washed away by cold water and spraying;

[0029] Oxalic acid treatment: immerse the disk in a 5% concentration of oxalic acid pool, shake and rotate the disk for 1-3 minutes;

[0030] Phosphating treatment: The plate element is immersed in a phosphate solution. The steel surface contacts the phosphate treatment solution, and the steel dissolves to form an insoluble compound, which adheres to the steel surface to form a film.

[0031] Lubricant treatment: It needs to react with metal soap to form a hard metal soap layer to increase its lubrication performance;

[0032] Rinse with clean water: remove the residue on the surface of the membrane to ensure that there is no residual chemical agent;

[0033] Drying: Dry the disk element to remove surface moisture and prevent rust.

[0034] Further: the coil needs to be surface treated before being soaked and pickled.

[0035] Furthermore, the hydrochloric acid concentrations in the three hydrochloric acid tanks increase successively, and the disk also gradually enters the hydrochloric acid tank with higher concentration successively from the low-concentration hydrochloric acid tank.

[0036] Furthermore, when the disk is cleaned in a clean water tank, it is necessary to shake and rotate the disk to ensure that it is thoroughly cleaned.

[0037] The present invention has the following advantages: the anchor nails of the present invention are subjected to fine wire drawing, cold heading and degreasing, and then softened and tempered so that the anchor nails can meet the mechanical performance requirements when welded with the steel lining of the nuclear power containment shell, thereby ensuring the quality stability of the nuclear power containment shell project. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The present invention provides a flow chart of a production process of anchor nails for nuclear power containment. DETAILED DESCRIPTION

[0039] The following is an explanation of the implementation of the present invention by specific specific examples. People familiar with this technology can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. It should be understood that these embodiments are only to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Technical engineers in this field can make some non-essential improvements and adjustments to the present invention based on the contents of the above invention; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] See also Figure 1 , a production process for anchor nails for nuclear power containment, comprising the following steps:

[0041] S1. Material coiling: suitable raw materials are hot-rolled or processed into coil shapes to obtain billets of suitable sizes.

[0042] S2. Pickling and phosphating can remove impurities remaining on the surface after the coiling treatment, and form a protective film with a lubricating effect on the surface of the material to ensure the subsequent drawing effect; the details of pickling and phosphating are as follows:

[0043] Surface treatment: First, the metal products are surface treated, including removing oil, rust and other impurities; because only a clean metal surface can ensure the effect of pickling and phosphating.

[0044] Immersion pickling: Immerse the entire coil in three hydrochloric acid tanks at room temperature and a concentration of 20%-25% for several minutes to remove the oxide film on the surface of the wire.

[0045] Removal of corrosion products: The pickled raw materials enter the flowing clean water tank, and the acid remaining on the surface of the material is washed away by cold water and spraying. During this process, the disc needs to be shaken and rotated to ensure thorough cleaning.

[0046] Oxalic acid treatment: Immerse the disc in a 5% concentration of oxalic acid pool, shake and rotate the disc for 1-3 minutes to increase the activity of the metal and make the film generated in the next process denser.

[0047] Phosphating treatment: The disc element is immersed in a phosphate solution. The steel surface comes into contact with the phosphate treatment solution, and the steel dissolves to form insoluble compounds, which adhere to the steel surface to form a film.

[0048] Lubricant treatment: Since the friction coefficient of the phosphate film is not very low and cannot provide sufficient lubricity during processing, it needs to react with metal soap (such as sodium soap) to form a hard metal soap layer to increase its lubrication performance.

[0049] Rinse with clean water: remove residues on the surface of the membrane to ensure that there are no residual chemicals.

[0050] Drying: Dry the disk element to remove surface moisture and prevent rust.

[0051] S3. Refined wire drawing: Use the refined wire drawing equipment to draw the phosphated wire. During the drawing process, the drawing speed, pulling force and other parameters need to be adjusted according to the material and specifications of the wire to ensure the drawing quality and efficiency. When the material is refined, the material changes from coarse to fine, and the material's structure changes, making the material's structure more compact, thereby increasing the tensile strength and yield strength, resulting in a small elongation of the material.

[0052] After the fine wire was drawn, the wire was subjected to tensile testing. The test results are shown in Table 1 below.

[0053] Table 1

[0054] time 1 2 3 4 5 6 Technology / / / / / / Resistance strength(Mpa) 644 618 624 598 629 620 Yield Strength(Mpa) 639 610 594 591 626 620 Elongation (A%) 10.00％ 10.50％ 12.00％ 12.00％ 10.50％ 8.50％ Shrinkage (Z%) 54％ 55％ 55％ 59％ 59％ 58％

[0055] After the above tests, the results showed that the material performance after fine wire drawing could not meet the product requirements.

[0056] S4. Cold heading; cold heading machine and mold are used to process anchor nails. During the production process of the cold heading machine, both ends of the anchor nails are subjected to force at the same time, and the rod of the anchor nail will cause stress removal, which will lead to different degrees of changes in the mechanical properties of the product. This change varies according to the expansion gap of the product rod diameter and the size of the chamfer.

[0057] At the same time, the anchor nails after cold heading were tested, and the test results are shown in Table 2 below.

[0058] Table 2

[0059] time 1 2 3 4 5 6 Technology / / / / / / Resistance strength(Mpa) 632 632 627 543 542 531 Yield Strength(Mpa) 599 427 551 537 451 453 Elongation (A%) 14.50％ 14.50％ 15.00％ 12.00％ 19.00％ 17.00％ Shrinkage (Z%) 54％ 53％ 53％ 57％ 59％ 62％

[0060] The above test results show that the mechanical properties of cold-forged anchor nails cannot meet the product requirements of anchor nails.

[0061] S5. Degreasing: In order to remove the residual oil on the surface of the anchor nails after cold heading, preheat the mesh belt furnace to 350-400℃, and then put the anchor nails into the mesh belt furnace to vaporize or burn the oil.

[0062] S6. Softening and tempering: put the degreased anchor nails into a constant temperature furnace for tempering, specifically: 580℃, 6 hours constant temperature tempering, and cooling with the furnace for 8 hours. After softening and tempering, the organizational structure of the anchor nails changes.

[0063] The anchor nails after tempering were tested, and the test results are shown in Table 3 below:

[0064] Table 3

[0065]

[0066] The above test results show that the mechanical properties of the anchor nails after softening and tempering meet the product requirements.

[0067] S7. Shot blasting: The anchor nails are sent into the shot blasting machine, and the steel shots are sprayed onto the surface of the anchor nails through the high-speed rotating shot blasting impeller. During the shot blasting process, the steel shots will hit the surface of the anchor nails at a high speed and a certain angle, thereby cleaning and strengthening the surface of the anchor nails.

[0068] S8. Rust prevention: soak the shot blasted anchor nails in the water-based anti-rust solution for about 1 minute, and then dry them. During the soaking process, ensure that each part is fully covered by the water-based anti-rust solution.

[0069] After many tests, it was found that this production process can avoid deviations in mechanical properties that may lead to adverse phenomena in nuclear power anchor nails.

[0070] The anchor nail production process of the present invention can produce anchor nails that meet the nuclear power containment steel lining welding standards.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A production process for anchor nails for nuclear power containment, characterized in that: The following steps are involved: S1. Material rounding: the raw material is initially processed into a round shape through hot rolling to obtain a billet of suitable size; S2. Pickling and phosphating to remove impurities remaining on the surface after the coiling treatment and form a protective film with lubricating effect on the surface of the material; S3. Fine wire drawing: Use fine wire drawing equipment to draw the wire after pickling and phosphating, so that the wire becomes thinner until it meets the requirements of the cold heading machine; S4. Cold heading: The anchor nails are processed by cold heading machine and mold. During the production process of the cold heading machine, both ends of the anchor nails are stressed at the same time, and the anchor nail rod will cause stress removal, which will lead to different degrees of changes in the mechanical properties of the product. S5. Degreasing: removing the oil remaining on the surface of the anchor nail after cold heading; S6. Softening and tempering: put the degreased anchor nails into a constant temperature furnace for tempering, specifically: 580°C, 6 hours constant temperature tempering, and cooling with the furnace for 8 hours; S7. Shot blasting; S8. Rust-proof.

2. The production process of anchor nails for nuclear power containment according to claim 1, characterized in that: In S5, the specific method of degreasing is: first preheating the mesh belt furnace to 350-400° C., and then placing anchor nails into the mesh belt furnace to vaporize or burn the oil stains.

3. The production process of anchor nails for nuclear power containment according to claim 1, characterized in that: In S7, the specific steps of shot blasting are: sending the anchor nail into the shot blasting machine, and spraying the steel shot onto the surface of the anchor nail through the high-speed rotating shot blasting impeller; during the shot blasting process, the steel shot will hit the surface of the anchor nail at a very high speed and a certain angle, thereby cleaning and strengthening the surface of the anchor nail.

4. The production process of anchor nails for nuclear power containment according to claim 1, characterized in that: In S8, the specific steps of rust prevention are: soaking the shot-blasted anchor nails in an aqueous rust-proof solution for 1-3 minutes, and then drying them. During the soaking, it is necessary to ensure that each part is fully covered by the aqueous rust-proof solution.

5. The production process of anchor nails for nuclear power containment according to claim 1, characterized in that: The specific method of pickling and phosphating is: Immersion pickling: Immerse the entire disk into three hydrochloric acid tanks at room temperature and concentration of 10%-25% for 1-8 minutes; Removal of corrosion products: The pickled raw materials enter the flowing clean water tank, and the acid remaining on the surface of the material is washed away by cold water and spraying; Oxalic acid treatment: immerse the disk in a 5% concentration of oxalic acid pool, shake and rotate the disk for 1-3 minutes; Phosphating treatment: The plate element is immersed in a phosphate solution. The steel surface contacts the phosphate treatment solution, and the steel dissolves to form an insoluble compound, which adheres to the steel surface to form a film. Lubricant treatment: It needs to react with metal soap to form a hard metal soap layer to increase its lubrication performance; Rinse with clean water: remove the residue on the surface of the membrane to ensure that there is no residual chemical agent; Drying: Dry the disk element to remove surface moisture and prevent rust.

6. The production process of anchor nails for nuclear power containment according to claim 1, characterized in that: The coil needs to be surface treated before being soaked and pickled.

7. The production process of anchor nails for nuclear power containment according to claim 5, characterized in that: The hydrochloric acid concentrations in the three hydrochloric acid tanks increase sequentially, and the disk gradually enters the hydrochloric acid tank with higher concentration sequentially from the low-concentration hydrochloric acid tank.

8. The production process of anchor nails for nuclear power containment according to claim 5, characterized in that: When the disk is cleaned in a clean water tank, the disk needs to be shaken and rotated to ensure thorough cleaning.

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